Diary of a Madman (1963)

Simon Cordier's a well-respected magistrate who visits a condemned prisoner, Louis Girot, just before his execution. Girot pleads his innocence insisting he's been taken over by a spirit which forced him to commit the crimes. Cordier doesn't believe him and the man suddenly dies. In the following days, Cordier must face a number of strange occurrences iand begins to wonder if he's now dealing with those same spirits.